Coherent high-velocity chiral magnons in the metallic altermagnet CrSb

TL;DR

This paper reports the discovery of coherent, high-velocity chiral magnons in the metallic altermagnet CrSb, demonstrating its potential for spintronic applications due to persistent spin-split magnons above room temperature.

Contribution

It provides the first observation of chiral spin splitting in a metallic altermagnet and characterizes its magnon dispersion with a minimal Heisenberg model.

Findings

CrSb exhibits highly dispersive antiferromagnetic spin waves with large group velocities.

Chiral spin splitting signatures are observed along the $ ext{Γ}$-$ ext{L}$ direction.

Magnons persist well above room temperature, indicating potential for spintronic devices.

Abstract

We report the collective magnetism of the metallic altermagnet CrSb. Magnetic susceptibility and polarized neutron diffraction measurements show that CrSb is a perfectly compensated Ising altermagnet below a N\'eel temperature of $T_N = 733(4)$ K. Inelastic neutron scattering experiments reveal coherent and highly-dispersive antiferromagnetic spin waves with large group velocities of 61(2) km s$^{-1}$ and 58(2) km s$^{-1}$ along the in-plane and out-of-plane directions, respectively. The observed magnon dispersions along high-symmetry directions of the Brillouin zone are well described by a minimal Heisenberg model up to third nearest neighbors of alternating antiferromagnetic and ferromagnetic character, $J_1 = 23(4)$ meV, $J_2 = -5.4(8)$ meV, $J_3 = 5.2(8)$ meV, and an Ising single-ion anisotropy term $D = 0.15(4)$ meV. We observe clear momentum space signatures of chiral spin splitting along the low-symmetry $\Gamma$-$L$ direction, characteristic of higher-order altermagnetic exchange interactions, the first such observation in a metallic altermagnet. These findings identify CrSb as a singular material: a metallic altermagnet in which coherent spin-split magnons persist well above room temperature, providing a compelling platform for spintronic applications.